Nitrate Removal from Aqueous Solution by Using Modified Clinoptilolite Zeolite

Background & Aims of the Study:  Nitrate is one of the most important pollutants that its reduced form, nitrite, can cause serious problems for human health and environment. Adsorption with cheap sorbents such as Zeolite is the best way for removal of this pollutant. So this study aimed to apply modified Clinoptilolite Zeolite for nitrate removal. Materials & Methods: Firstly, Clinoptilolite zeolite was screened by 1-2 mm sieves for monolithic of it. Then zeolite was boiled in HCL 20% for 3 hours for removal of Carbonate and impurities present in zeolite structure and increase of porosity and purity of zeolite. Finally, the zeolite was dried in temperature of 300°C to evaporate the water present in zeolite structure and increase the absorbability. After the modification of the Zeolite, the effects of pH, time, strings speed, optimum amount of adsorbent in Nitrate removal were investigated and optimized by one factor at the time method. Also reaction kinetics and isotherms were determined. Results: This study indicated that the optimum condition for Nitrate removal by means of modified zeolite as adsorbent is pH=5, contact time of 180 minutes and adsorbent amount of 16 g/l. The investigation of isotherm and kinetic equations indicated that Nitrate adsorption follows Langmuir and pseudo first order, respectively. Conclusions: The zeolite modified by HCL and heat has a higher efficiency in Nitrate removal compared to simple zeolite, because of losing its hydroscopic water and having larger sites, although in total it doesn’t have sufficient efficiency for Nitrate removal.